Protein and nonionic agent compositions



PROTEIN AND NORTGNIC AGENT QOMPQSITEONS Harold K. Salzherg, Bainbridge, N.Y., and Clifiord J. King, Mexico City, Mexico, assignors to The Borden Company, a corporation of New Jersey N Drawing. Application September 11, 1957 Serial No. 683,225

9 Claims. c1. tee-12s This invention relates to a protein composition including an agent for releasing microscopic bubbles of gas, in order to eliminate fish-eyes, pinholes, and surface roughness in films and coatings made from the composition.

The application is a continuation-in-part of our application .Serial No. 455,339, filed September 10, 1954, for Clay Dispersions, now abandoned.

The invention is particularly useful in coating paper and fabricsand especially paper requiring evenness of surface and freedom from flaws for offset lithography and other uses.

In such coated paper, casein is a usual binder or adhesive film forming component and a filler, such as finely divided mineral material, is present in large amount. The coating film frequently shows bubbles of air, from the aqueous dispersion applied to produce the coating, that become set in the film as it dries until the composition is too stiff or non-flowable to fill the space even if the bubbles eventually escape. Also there are microscopic pinholes (craters extending into the dried film) and surface roughness detectable by rubbing the finger over the surface. Although these imperfections vary in extent from lot to lot of the coated paper and although many cxpedients have been'tried to avoid the difiiculties, they still constitute an unsolved problem in making high grade coated paper.

Among the expedients tried is the incorporation of various defoatning agents. These decrease the number of large bubbles of air appearing as visible foam on the aqueous solution of the casein and other materials at the time of their agitation and solution in water. Use of defoamers, however, may sometimes cause a second type of defect to appear in the coating in the form of undispe'rsed defoamers. Such defects are variously referred to as oil spots or fisheyes.

We have now discovered means and composition for so making the protein solution that the finished dried film is substantially free of fish-eyes and pinholes and is satisfactory in smoothness of surface for exacting uses such as in offset lithography.

Briefly stated our invention comprises the herein described combination of alkali soluble protein and a nonionic surfactant applied to the protein in such manner as to be difiicultly extractable therefrom and, in such association with the protein, to serve as a release agent for microscopieair bubbles otherwise retained by the protein in aqueous solution and in films made therefrom. The invention includes the process of making this combination and also coatings and films of it. p

In general, the bubble release agent is mixed into the protein in dry condition. The mixing is made intimate and is continued until the agent, normally extractable by ether or like organic solvent, becomes more difi'icultly extractable and in part not extractable at all in usual laboratory extraction technique. After a time, the protein and the thus oiled on agent are dissolved in Water. The product so made, when it is to be used for coating paper, for instance, may be mixed with a large propor- 2,933,406 Patented Apr. 19, 1960 2 tion of clay filler and coated on paper without creating the difiiculties described above. Also, dry gelatin with the agent oiled on and then dissolved may be used to make a solution for use in making films of gelatin supported.

photographic emulsions.

Once the effects of the nonionic or bubble release agent, applied as described, have been observed, various theoriesv may be advanced to explain the result obtained. We con-- sider that an important part of the result is due to the combination or close association of the said agent with the casein that is established when the two are mixed or That the two adhere or remain bound together is shown by the non-extractarubbed together in the dry state.

bility of the agent in part after the mixing is completed.

As a consequence of the close and remaining association,

the agent causes the casein to shed microscopic air bubbles: which would otherwise cause the microscopic pinholes and fish-eyes in the finished coating. Also the nonionic agent of kind described acts as a setting retarder for the protein. time of setting of soy proteins, for example, with the nonionic present than otherwise. This gives a longer period as the film or coating composition dries, during which the microscopic bubbles may escape.

More specifically, the period for setting to non-flowable form was lengthened from 600 seconds to 720 seconds in a representative treatment of soy protein and, in the case of an animal glue, to 5 times the setting time for the untreated glue.

As to materials, the protein used is any one that is alkali soluble, that is, soluble in water with alkali in amount to establish the pH at 8-8.5 or moderately higher. Examples are casein, gelatin, and isolated soy protein. The protein may be one that is moisture proofed in advance, as by being worked in damp condition with zinc carbonate or with zinc oxide and ammonium chlorid and then dried. I

The bubble release agent is a water and ether soluble nonionic surfactant. Examples that are satisfactory and illustrate the general class to be used .are the agents 5 selected from the group consisting of water. soluble surface active ethers, esters, ether-esters, and ether-alcohols.

oxyethylene derivatives of any of the esters named above.

The proportion of the oxyalkylene in any of the cornpositions above may be varied, as from 4-20 units and usually 8-20 per mole of the product. In general, molecular complexity is desirable in the bubble release agent, so long as the agent retains its solubility in water.

Commercial products illustrating the class of bubble release agent and thatwe have used to advantage are Spans (C -C higher fatty acid partial esters of hexitol anhydrides), Tweens (polyoxyalkylene derivatives of Spans), Igepal CTA (aromatic polyglycol ether), Pluronic s L64 (a liquid polymeric ether-alcohol such as the ethylene oxide derivative of propylene glycol of m.w. about 1500-1800 (corresponding to a molecular weight after alkoxylation of about 3,000) and ethylene oxide content 40%50%, that maybe prepared as described in U.S. Patent 2,677,700), Antarox (aromatic polyglycol ether), Triton (an alkyl aryl polyetber alcohol), Sterox (a polyoxyethylene thioether), Myverol (glycerol monostearate), Myrj (polyoxyethylene stearate), Brij (polyoxyethylene lauryl alcohol), Nopalcol (ethylene oxide condensate-with a fatty acid), and Surfynol (di-' tertiary acetylenic glycol derivatives).

each other.

Thus We have found a longer Tributyl citrateJoc tyI alcohol, tricresyl phosphate, pine oil, and other defoamers of known effectiveness in de-,

creasing macroscopic foam may be used in combination 7 with one or more of the release agents for microscopic bubbles. We have found particularly satisfactory a mixture of equal parts of Pluronics L64, Triton 100,

The amount of alkali required is usually about 2%--10% of the Weight'of casein or soy protein. The gelatin composition is used in neutral condition. y

When a filler is used, as in making a coated magazine paper, .clay' is the only filler that we have found to be satisfactory. The clay may be a fine white claysuch as china clay or kaolin. With the commonly used precipitated, finely divided calcium carbonate, on the other hand, roughness of surface results.

Auxiliary additives to paper coating colors may include pyrophosphate or polyphosphates commonly used in in? dustry. The dispersant, present in amount of only a fraction of 1% of the clay, fiuidizes the clay-water paste permitting the use of much less water than is otherwise necessary. A typical clay slip may comprise as little as 1 pm: of water to 2 parts of clay by weight, but usually a somewhat greater proportion of Water than this is used.

materials to soften the'coating and introduce flexibility to the coated sheet, such as glycerol, glycols, or synthetic lattices. The color may also include a low percentage of a protein hardener, designed to moisture-proof the coated sheet, such materials usually coming from the class of aldehydes or metal salts such 'as aluminum acetate. These auxiliary ingredients are in no Way detrimental to the successful performance of the wetting agent in removing microscopic foam pits from the coating.

As to proportions, the following table shows proportions that are used for best commercial results and wider ranges that may be'used'for some purposes.

Parts by Weight Component 1 I Commercial Permissible Protein, dry weight 100 100 Microscopic bubble release agent. 1-5 110 Alkali to establish pH 84) Above 8 Trlbutyl citrate 1-5 1- lay (for paper coatin 250-500 100-2. 000 Water To give desired concentration of solution.

The clay is omitted entirely for such purposes as making graphic'film. As to conditions, the casein. or other protein is mixed a casein coating containing no filler or a gelatin photoin powdered and dry-condition, that is, at a moisture content not substantially above with the bubble release agent. We find a little moistureto be helpful at this stage and normally work at about 5%15% of" water on the weight of the selected protein.

Ambient. temperatures are satisfactory for the mixing.

Conventional equipment is used for the mixing, as for example ribbon or screw conveyor mixers through which the protein is being moved and into which the agent is introduced and the agent distributed in any convenient manner. Such equipment not only mixes but alsorubs the bubble release agent on and into the mass of powdered protein. The mixing is continued for a substantial time, as for example 5-60 minutes. In this manner, the agent isso fixedto casein, for example, as to cause interference with subsequent extraction, of the agent so oiled on becoming nonrextractable by ether in a representative preparation. v j' The clay, when used, is best made into aslip before itsincorporation, as follows: The clay is first wet with i water with the help of a dispersant such as the sodium coating which are undesirable in the usual applications Titanium dioxide or other pigment may be mixed with the clay. v

If a mixture of two or more of the nonionic agents is used, they are suitably introduced together into the dry casein as described.

The invention will be further illustrated by the following specific examples of the practice of it, all proportions here and elsewhereherein being expressed as parts by weight unless specifically stated to thecontrary.

EXAMPLE 1 A lactic acid grade of powdered casein and normal analytical values with respect to moisture (about 7%), ash and fat content was treated with a nonionic surface active polymeric ether-alcohol (Pluronics L64). The liquid agent was sprayed onto the casein granules while being tumbled. The agent was prewarmed to a temperature of about 50 C. which reduced its viscosity to the point of easy handling in spraying equipment and then applied as a spray in the proportion of 2 lbs. of the agentto of the casein in the tumbler, all equipment being conventional. The treatedcasein-was dissolved in water using ammonia .as the. alkali in amount to provide a pH of 8.0 for a 20% solution.

Upon'application of a foaming test, based upon rapid. agitation of 200 ml. of the solution in a Waring blender;

the solution developed only 40 ml. of foam as against ml. by untreated casein of the same lot in a cornparable test. This reduction in foam, though desirable,

was not the objective sought, however, in" treating the casein, as the gross foam is not indicative of themicro- .scopically dispersed air. A second test was applied, this one on a film" of the" casein which had been preparedv by coating paper at a liquid thickness of 0.02 inch and then drying under room conditions. The film of treated casein, when viewed under the-microscope at 25 magnifications, showed only a very few pinholes present. Ajcompanion film made from casein that had not been mixed with the L64 revealed numerous pinholes, i.e.' microscopic voids in the of casein by industry.

EXAMPLE 2' In order to improve the film still further, the nonionic agent L64 was supplemented by the addition of 1 part; oftributyl citrate defoarner for 100 of the casein, .in

the composition of Example 1. 'There was complete elimination of pinholes in the casein coating on the paper. There were, however, some oil spots due to over-concentration ofthe tributyl citrate in localized areas. 7

EXAMPLE 3 Half of the Pluronics L64 of Example Z'Was replaced by Triton 1G0, making the agent oiled .onto the casein a combination of equalparts of Pluronics L64, Triton 100, and tributyl citrate. a

- The resulting product, when dissolved'in alkaline, water and used as the bond for clay in the coating of paper,

' produces a film whose surface is free of both the pinholes and oil spots.

EXAMPLE 4 loisture-proofed zinc casein was prepared byfworkaing damp casein 100 parts on the dry basis with zinc carbonate 5 parts, according to US. Patent 2,103,153 tojDunham and the granulated product then substituted on an equal weight basis for the casein in the composition and procedure of Example 1.

The final product, used as the binder for clay in the coating of paper for making offset duplicating plates, eliminates pinholes in the coating and also imparts the correct degree of water resistance to the coating.

6 EXAMPLE 8 In order to ascertain the comparative effect of the treatment with the nonionic Example 1, by the process thereof, upon difierent types of industrial proteins, casein,

EXAMPLE 5 5 isolated soy protein, and powdered animal glue were so treated in the same experiment. Ammoniacal solutions The COmbiflatiOH 0f Propertles referred to In Example of the products showed the following values as to pH, 4 w s 6150 Obtained y tfefitlng a y mlXtuIe of viscosity, volume increase on agitating in the Waring P3115 of casein, 3 0f Zimc OXlde, and 4 0f afnmomum blender and pinholes in the dried film made from the chloride with the mixture of the three HOmOmC 0f E solutions. These values are set alongside the correspondample 10. A solution of the product in water containing ing values for the untreated proteins in the following ammonia gives a film which, when dried, contains no table, in order to bring out the substantial improvements microscopic voids and furthermore exhibits a substantial resulting from the treatment.

Casein Soy Protein Animal Glue Properties Treated Un- Treated Un- Treated Untreated treated treated solution, pH 9. 5 9. 5 9. 6 9. 5 7. 0 6. 9 Viscosity, cps 2,300 4,200 500 420 140 130 Volume increase, percent" 8 19 42 61 15 115 Pinholes in film None Some None Some None Many degree of resistance to the softening effects of water EXAMPLE 9 or water vapor.

EXAMPLE 6 The product of Example 5 which, as a clear protein film had appeared free from pinholes and had shown a high degree of water resistance, was used as the vehicle a in a suspension of clay of paper-coating grade, the composition being made up in stages with the proportions of the several components as follows:

A. Treated casein:

Casein, 24-mesh 100 Nonionic L64 1 Nonionic Triton 100 1 Defoamer (tributyl citrate) 1 Zinc oxide 4 Ammonium chloride 3 B. Casein solution:

Treated casein A 18.3

Water 89.0 Ammonia, 26 B 2.7

C. Clay coating.

Casein solution B 50.9 Clay (ASP-600) 42.1 Water 17.9

f The coating was of composition and viscosity suitable for application to paper on a commercial roll coater, and was so used to obtain a decorative effect upon this relatively low cost grade of paper.

EXAMPLE 7 Treatment Ex. 2 Ex. 3 None Volume increased due to foam, percent 19 120 Pinholes None None Many It will be noted that the percentage decrease in pinholes was out of proportion to the decrease in total foam.

Casein was treated dry with a nonionic wetting agent in the proportion of 2 parts of Pluronics L64 to parts of casein. Intimate admixture of the agent with the casein was accomplished by passing the mixture through differential speed rolls maintained at an elevated temperature. This processing subjects the ingredients to heat and pressure. The product was used in preparing a clay-dispersion containing, for 20 parts dry weight of casein dissolved in ammoniacal water, 98 of clay, 0.2 part of Igepal CTA, 0.34 part of tetrasodium pyrophosphate, and total water 177 parts.

EXAMPLE 10 A dispersion of a widely used paper coating clay in water was combined with a water dispersion of soybean protein which had been previously treated with the nonionic agent, Pluronics L64, and with a well-known defoamer, tributyl citrate. The protein used here is obtained by the extraction with mild alkali of soybean meal. The protein curds out from solution upon treatment with acid and isprepared for commercial use by washing, drying and grinding. 100 parts of the dry powder was oiled with 2 parts of Pluronics L64 and 1 part of tributyl citrate, by weight. The treated protein was then dissolved in ammoniated water and solution combined with the clay slip, the ingredients and proportions being:

Parts Clay ASP 600 375 Water A 375 Tetrasodium pyrophosphate 0.75 Treated soy protein 50 Ammonia 52 Water B 250 EXAMPLE 11 The experiment of Example 10 was repeated using a grade of gelatin such as might be used in coating photographic printing paper, to replace the casein on an equal weight basis. This gelatin served as the pigment binder in the same manner as the other proteins. Again the coating revealed no pinholes oreraters when viewed at a magnification of 20X.

EXAMPLE 12 EXAMPLE 13 The composition and procedure of Examples 2 and 12 were followed in turn with the replacement of the tributyl citrate there used by an equal weight of any of the other defoamers described herein, on an equal weight basis.

EXAMPLE 14 with a mixture of 2 parts of Pluronics L64 and 1 part of. The cooled solution was coated onto;

tributyl citrate. paper and observed as to gel formation as drying progressed. When the marks of a comb pressed repeatedly into the coating would no longer disappear upon withdrawal of the comb, the coating was judged to have attained gel structure. The paired values in'seeonds were as follows:

It is to be understood that itis intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of illustration which do not constitute departures from the spirit and scope of the invention.

We claim:

1. In making a coating and film fonning composition fen use in aqueous solution, to leave on drying a film substantially free from microscopic pinholes and other imperfections caused by retained air, the process which comprises mixing an adhesive consisting essentially of alkali soluble protein in dry form containing not more than 15% of water on the weight of the protein and selected from the group consisting of casein, soy protein, and gelatine with a nonionic surfactant serving as a bubble release agent and selected from the group consisting of Waterand ether-soluble surface active ethers, esters, ether-esters, and ether-alcohols in the proportion of 1-10 parts by weight for 100 parts of the protein, and maintaining the contact between the protein and the nonionic surfactant and continuing the mixing in dry condition until the agent becomes in part non-extractable from the mixture by ether.

2. The process of claim 1 in which the proteinis casein. 3. The process of claim 2 in which the casein and bubble release agent are mixed with clay.

4. A coating and film forming composition compris ing a mixture of an adhesive consisting essentially of an alkali soluble protein in dry form containing not more than 15% of water on the weight of the protein and selected from the group consisting of casein, soy protein,

and gelatine with a nonionic surfactant selected from the group consisting of waterand ether-soluble surface active ethers, esters, ether-esters, and ether-alcohols in the P 19- portion of l-lO parts by weight for 100 parts'of the pro- Soy Protein Animal Glue Photographic Gelatin Un- Treated Un- Treated Un- Treated treated treated treated on Formed (see) 600 720 120 600 0 26 The release of microscopic air bubbles, responsible for pinholes, in a clay coating, would be expected to be faster from a coating in which gel formation on the sheet was delayed; when the coating gels there can be no further escape of bubbles. V

The same observation can be made by comparing the viscosity values ofliquid coatings made with untreated and treated casein. The lower the viscosity, the more readily can air bubbles escape. The treatment of casein in one experiment with 2% of Pluronics L64 before preparing a clay coating reduced the viscosityof the coating from 4 seconds to 3.2 seconds 'for' 100 revolutions on the Stormer viscometer.

Extraction of treated casein That the nonionic agent reacts to some degree with the dry protein during the treating processisjndicated by the results of solvent extraction testson casein treated withthe polymeric glycol ether-alcohol agent (1.64) and tributyl citrate (the treatment of Example 2). Whereas ether in the Soxhlet apparatus-should have extracted 3.0% of added material.(l2% of nonionic and 1% of tributyl citrate) plus the extractable fat from the casein, substantially less extract was obtained.

AVERAGE OF ETHER EXTRACTION RESULTS BY SOXHLET AND ROSE-GOTTLIEB TECHNIQUES Percent Extracted from untreated casein 1.0 Extractable nonionics added to casein 3.0 Extractable from mixed product, calculated 4.0 Actually extracted 2.75 Nonionic material bound rby casein 1.25

sition of claim 4 and finely divided clay admixed thereinto in the proportion of -2000 parts by weight for- 100 parts or" the protein.

6. The composition of claim 4, the proteinbeing casein. 7. The composition of claim 4, the protein being casein and the nonionic surfactant being a polymeric etheralcohol of mean molecular weight about 3000 and ethyl ene oxide content about 40%-50% of the weight of the surfactant. i

8. The process of claim 1 which includes mixing into the said composition a defoamer selected from the group 7 consisting of tributyl citrate, octyl alcohol, tricresyl pliesphate, and pine oil.

9. The composition: of claim ,4, the said gelatine.

References Cited inthe file of this patent UNITED STATES PATENTS 2,220,700 Atwood Nov; ,5, 1940 2,695,892 Jaccard et al. Nov. 30, 1954'- 2,709,689 Herzog May 31, 1955 2,776,904 Brown Jan. 8, 1957 2,810,655 Dean Oct. 22, 1957 p t i b in Knox et a1. Apr. 22, 1958 

1. IN MAKING A COATING AND FLIM FORMING COMPOSITION FOR USE IN AQUEOUS SOLUTION TO LEAVE NON DRYING A FLIM SUBSTANTIALLY FREE FROM MICROSCOPIC PINHOLES AND OTHER IMPERFECTIONS CAUSED BY RETAINED AIR, THE PROCESS WHICH COMPRISES MIXING AN ADHESIVE CONSISTING ESSENTIALLY OF ALKALI SOLUBLE PROTEIN IN DRY FORM CONTAINING NOT MORE THAN 15% OF WATER ON THE WEIGHT OF THE PROTEIN AND SELECTED FROM THE GROUP CONSISTING OF CASEIN, SOY PROTEIN, AND GELATINE WITH A NONIONIC SURFACTANT SERVING AS A BUBBLE RELEASE AGENT AND SELECTED FROM THE GROUP CONSISTING OF WATER- AND ETHER-SOLUBLE SURFACES ACTIVE ETHERS, ESTERS ETHER-ESTERS,AND ETHER-ALCHOLS IN THE PORTION OF 1-10 PARTS BY WEIGHT FOR 100 PARTS OF THE PROTEIN, AND MAINTAINING THE CONTACT BETWEEN THE PROTEIN ANS THE NONIONIC SURFACTANT AND CONTINUING THE MIXING IN DRY CONDITION UNTIL THE AGENT BECOMES IN PART NON-EXTRACTABLE FROM THE MIXTURE BY ETHER. 